Media captionSchaft won this round of Darpa's competition by a wide margin

A robot developed by a Japanese start-up recently acquired by Google is the winner of a two-day competition hosted by the Pentagon's research unit Darpa.

Team Schaft's machine carried out all eight rescue-themed tasks to outscore its rivals by a wide margin.

Three of the other 15 teams that took part failed to secure any points at the event near Miami, Florida.

Schaft and seven of the other top-scorers can now apply for more Darpa funds to compete in 2014's finals.

Darpa Robotics Challenge Scoreboard

1. Schaft (27 points)

2. IHMC Robotics (20 points)

3. Tartan Rescue (18 points)

4. MIT (16 points)

5. Robosimian (14 points)

6. Traclabs / Wrecs (11 points)

8. Trooper (9 points)

9. Thor / Vigir / Kaist (8 points).

12. HKU / DRC-Hubo (3 points)

14. Chiron / Nasa-JSC / Mojavaton (0 points)

Darpa said it had been inspired to organise the challenge after it became clear robots were only capable of playing a very limited role in efforts to contain 2011's Fukushima nuclear reactor meltdown in Japan.

"What we realised was ... these robots couldn't do anything other than observe," said Gill Pratt, programme manager for the Darpa Robotics Challenge.

"What they needed was a robot to go into that reactor building and shut off the valves."

In order to spur on development of more adept robots the agency challenged contestants to complete a series of tasks, with a time-limit of 30 minutes for each:

Image caption
The robots had to steer a car along an obstacle-lined course

Drive a utility vehicle along a course

Climb an 8ft-high (2.4m) ladder

Remove debris blocking a doorway

Pull open a lever-handled door

Cross a course that featured ramps, steps and unfastened blocks

Cut a triangular shape in a wall using a cordless drill

Close three air valves, each controlled by a different-sized wheel or lever

Unreel a hose and then screw its nozzle into a wall connector

More than 100 teams originally applied to take part, and the number was whittled down to 17 by Darpa ahead of Friday and Saturday's event.

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Media captionHumanoid robots drove cars, climbed ladders - and often fell - in the competition sponsored by the US Department of Defense

Some entered their own machines, while others made use of Atlas - a robot manufactured by another Google-owned business, Boston Dynamics - controlling it with their own software.

One self-funded team from China - Intelligent Pioneer - dropped out at the last moment, bringing the number of contestants who took part at the Homestead-Miami Speedway racetrack to 16.

Image caption
Schaft's liquid-cooled robot was able to carry out all of the eight main challenges it faced.

Schaft's 1.48m (4ft 11in) tall, two-legged robot entered the contest the favourite and lived up to its reputation.

It makes use of a new high-voltage liquid-cooled motor technology that uses a capacitor, rather a battery, for power. Its engineers say this lets its arms move and pivot at higher speeds than would otherwise be possible, in effect giving it stronger "muscles".

Image caption
The robots had to attach a hose pipe as one of their challenges

The machine was developed by a spin-off from the University of Tokyo's Jouhou System Kougaku lab, which Google recently revealed it had acquired.

The team scored 27 points out of a possible 32, putting it seven points ahead of second-placed IHMC Robotics, which used Atlas.

Scores were based on a system that awarded three points for completing a task's primary objectives, and then a bonus point for doing so without any human intervention.

Schaft's robot behaved nearly perfectly, but lost points because "the wind blew a door out of their robot's hold and because their robotic creation was not able to climb out of a vehicle after it successfully navigated an obstacle course," reported the Japan Daily Press.

'Reality check'

Videos posted online by Darpa illustrate that the robots remain much slower than humans, often pausing for a minute or more between actions while they carried out the calculations needed to make each movement.

Several proved unsteady on their feet and were only saved from falls by attached harnesses.

Three of the teams which entered self-designed machines - including Nasa's Johnson Space Center and its robot Valkyrie - failed to complete any of the challenges.

The event was described as a "reality check" by Jyuji Hewitt, who attended on behalf of the US Army's Research, Development and Engineering Command.

Image caption
The robots - including Nasa's Robosimian - were protected by harnesses on case they fell

But Darpa's Mr Pratt added that the competition, and the finals that will be held in December, would help bring forward a time the machines could be used in real-world situations.

"Today's modest progress will be a good next step to help save mankind from disasters," he said.

The top eight teams can now apply for up to $1m (£611,000) of Darpa investment before the finals to improve their robots' skills. The winner will get a $2m prize.

Lower scorers in last weekend's round can stay in the contest but will have to fund their own efforts,